This invention relates to position indication for a rotary valve actuator which is used to open or close a rotary valve. More specifically, the invention is directed to apparatus for providing a visual and electrical indication of whether or not a rotary valve is in the open or closed position.
It is known to use pneumatic and hydraulic pressure to operate a rotary valve actuator by applying fluid under pressure to a valve actuator through pneumatic or hydraulic fluid lines. For example, there is known in the art a type of rotary valve actuator having opposing pistons which are coupled to a rack and pinion mechanism for converting pneumatic or hydraulic pressure applied to the pistons to torque for opening and closing a rotary valve.
The rotary valve has a valve member which is directly connected to the output shaft of the rotary actuator and is selectively rotated into and out of the path of fluid flow between the inlet and outlet ports of a valve housing, between open and closed positions which are typically ninety degrees apart. Although the open or closed state of a rotary valve may be indirectly determined by sensing fluid pressure or flow downstream of the valve, it is desirable to have a direct indication of whether a valve is open or closed, independently of fluid flow through the valve. A direct indication of the open or closed state of a rotary valve can be provided from a visual observation of the angular position of the output shaft on the rotary valve actuator relative to a fixed reference, since the output shaft of the rotary valve actuator is directly connected to the valve member.
It is known in the art to couple a position indicator to the output shaft of the rotary valve actuator for pointing in one direction corresponding to the open state of the valve and another direction for the closed state. However, prior art devices are difficult to see from a distance. Moreover, they can only be viewed from a limited number of directions. Also, prior art valve position indicators are not readily adaptable for mounting on rotary actuators having shafts of varying length, shape and angular disposition. For successful mounting and use, prior art position indicating devices require shims, brackets and seals to accommodate different shaft heights and diameters and realignment of the rotary actuator output shaft to accommodate any angular misalignment.